Azotriazole and azotetrazole antifog, antistain and selective desensitizers for silver halide emulsions

ABSTRACT

Azotriazoles and azotetrazoles are effective anti-fogging agents, anti-stain agents and selective desensitizers for silver halide photographic emulsions. Such agents may be employed in reactive association with the emulsions, or in a processing bath prior to or during development of emulsion layers.

United States Patent Baldassarri et al.

AZOTRIAZOLE AND AZOTETRAZOLE ANTIFOG, ANTISTAIN AND SELECTIVE DESENSITIZERS FOR SILVER HALIDE EMULSIONS Inventors: Agostino Baldassarri, Savona', Luigi Cellone, Albissola MarinaSavona, both of Italy Assignee: Minnesota Mining and Manufacturing Company, St. Paul, Minn.

Filed: Mar. 15, 1972 Appl. No: 235,011

Published under the Trial Voluntary Protest Program on January 28, 1975 as document no. B 235,011.

Foreign Application Priority Data Mar. 16, l97l ltaly 49093/71 US. Cl. 96/109; 96/665; 96/56 Int. Cl. G03C 11'34 Field of Search 96/109, 66.5, 66.4, 56;

Primary Examiner-Norman G. Torchin Assistant Examiner.lohr1 L. Goodrow Attorney, Agent, or Firm-Alexander, Sell, Steldt & DeLaHunt [57] ABSTRACT Azotriazoles and azotetrazoles are effective antifogging agents, antistain agents and selective desensitizers for silver halide photographic emulsions, Such agents may be employed in reactive association with the emulsions, or in a processing bath prior to or during development of emulsion layersv 12 Claims, No Drawings AZOTRIAZOLE AND AZOTETRAZOLE ANTIFOG, ANTISTAIN AND SELECTIVE DESENSITIZERS FOR SILVER HALIDE EMULSIONS The present invention relates to the use of azotriazoles and azotetrazoles as anti-fog, anti-stain and/or selective desensitizers for silver halides photographic emulsions.

Various compounds have long been employed to reduce fog and stain in silver halide emulsions. Certain of these compounds must be contacted with silver halide photographic emulsions in order to effectively inhibit fog; others are desirably employed in processing baths through which silver halide emulsions pass during or prior to development. Certain fog inhibiting compounds in addition tend to desensitize silver halide emulsions. Those desensitizers which desensitize silver halide only to radiation of certain wave lengths, for example, X-rays, are known as selective" desensitizers, and are particularly useful in silver halide radiographic emulsions.

Many of the compounds which can effectively inhibit fog are unfortunately incapable of similarly inhibiting stains (i.e., intense, localized fog centers). Further, certain fog-restraining compounds can be employed only in a silver halide photographic emulsion (US. Pat. No. 2,273,152), whereas other compounds can be employed only in photographic processing baths. Moreover, many fog inhibiting compounds do not function as selective desensitizers for silver halide emulsions. It would be highly desirable to provide a single class of compounds capable of restraining fog, restraining stains", and of selectively desensitizing silver halide emulsions.

It has now been found that azotriazole and azotetrazole compounds are capable of inhibiting fog when placed in contact with a silver halide emulsion (as by being placed in the emulsion, in a layer adjacent the emulsion, or by being placed in a processing bath which is employed prior to or during development of the emulsion). These compounds have also been found to inhibit stains in silver halide photographic emulsions, and, in larger quantities, to selectively desensitize silver halide emulsions.

Accordingly, in one embodiment the present invention relates to a silver halide photographic emulsion having contacted therewith at least a fog-inhibiting amount of an azotriazole or an azotetrazole. In another embodiment, the invention relates to a method for in hibiting fog in a silver halide photographic emulsion which comprises contacting the emulsion with an azotetrazole or an azotriazole. In yet another embodiment, the invention relates to an aqueous processing solution for silver halide photographic emulsions adapted for use prior to or during development and containing from about 3 to about 6 milligrams of an azotriazole or an azotetrazole per liter of solution.

The azotriazoles and azotetrazoles of the present invention preferably correspond to the formula 2 z' I c N N c N l N wherein Z and Z independently represent atoms forming heterocyclic nuclei of the triazole or tetrazole series. By azotriazole" and azotetrazole", reference is made to compounds which have respectively two triazole heterocyclic nuclei or two tetrazole heterocyclic nuclei, which nuclei are joined by an N=N linking group through carbon atoms thereof. These compounds may be variously substituted, and it has been found that azotriazoles and azotetrazoles as a class generally exhibit anti-fog, antistain and selective desensitization characteristics. In a preferred embodiment, sub stituents borne by the heterocyclic nuclei of the azotriazoles and azotetrazoles of the invention include hydrogen, alkyl (e.g., C,C alkyl), alkaline (e.g., C C and aryl (e.g., phenyl, naphthyl, including substituted aryl such as alkaryl having no more than 15 aliphatic carbon atoms, etc.). Accordingly, in a most preferred embodiment the azotriazoles and azotetrazoles of the present invention correspond to the formula wherein X is carbon or nitrogen, and each Y group independently represents a hydrogen atom, an alkyl group (e.g., C,C an alkaline group (e.g., C,C or an aryl group (e.g., phenyl, naphthyl, including substituted aryl such as alkaryl containing no more than 20 aliphatic carbon atoms), etc.

In comparison with known fog restrainers, the present invention permits a single class of fog restrainers to be used for many purposes. For example, the triazoles and tetrazoles of the invention are useful both in photographic silver halide emulsions, (e.g., mixed into the emulsion layer or employed in a layer adjacent the emulsion layer) and in photographic processing baths which, for example, are employed either prior to development (as a pre-bath), in the developing bath itself, etc. The azotriazole and azotetrazole compounds of the invention are particularly desirable because they are generally readily soluble in common photographic solvents such as water, alcohol, and aqueous alkaline solutions such as developer solutions. It will further be understood that it is most desirable to use highly soluble azotetrazoles or azotriazoles of the invention when they are to be employed in photographic processing baths, and to use the less soluble azotriazoles or azotetrazoles when they are to be used in an emulsion layer or in a layer adjacent an emulsion layer.

The invention may be more easily understood by reference to the following illustrative, non-limiting examples.

EXAMPLE 1 5,5'-azotetrazole-1,l 'pentahydrate disodium salt Na-N-CN=,N-CN-Na -5HO n l l 2 l N N N N N/ Analysis: Calculated Found EXAMPLE 2 5,5 'azotriazole hemihydrate NIT-C N N c ar i l l l l H N N N N H- H20 C 2 (prepared according to B. 26 2600 J. Thiele and K. Heidenrich) 8.4 g of 3-amino-l,2,4-triazole (0.] moles) were dissolved by boiling in l cc of H 0 containing 16 g (0.4 moles) of NaOH in a 300 cc flask equipped with mechanical stirrer and reflux apparatus. 5.4 g of KMnO in powder form were slowly added, with caution, to this solution. The excess oxidant was cautiously eliminated by addition of a few drops of ethanol. The mixture was filtered under vacuum and the yellow liquid obtained was acidified at C with glacial acetic acid. A very fine, pale-yellow powder was separated and collected by filtering and dried under vacuum. Yield: 2 g.

This compound can be usefully introduced into a photographic emulsion or photographic bath in aqueous solutions of sodium carbonate or NaOH.

- N N N A solution containing 9.8 g of amino-methyl-triazole (0.1 moles) prepared according to B. 26 2599, J. Thiele and K. Heidenreich), 16 g of NaOH (0.4 moles) and 100 cc of H 0, was brought to the boil in a 500 cc flask equipped with mechanical stirrer and reflux apparatus. Powdered KMnQ, was cautiously added in small amounts until the solution became permanently green (5.5 g of potassium permanganate). The excess oxidant was eliminated by addition of a few drops of ethanol. The separated brown manganese dioxide was filtered under vacuum. The cooled yellow solution was acidified (t 15C) with glacial acetic acid. A sulfur-yellow, very fine powder separated out and was filtered, dissolved in NHqOH, precipitated with CO and washed with H O. Yield: 2 g.

This compound can be usefully introduced into an emulsion or photographic bath in solutions of sodium carbonate or NaOH.

Analysis: Calculated Found N% 58.33 57.94 C% 37 .50 37.23 HFv 4.20 4. 3 1

EXAMPLE 4 l l '-diphenyl-5,5 'azotetrazole (prepared according to Journ. Prakt. 2, 134 282, R. Stolle).

20 g of l-phenyl-5-amino-tetrazole (prepared according to CA. 65 20137h, C.D. Bassinger and Takashi Enkoji) were dissolved in 500 cc of boiling water in a 2 liter flask equipped with a mechanical stirrer and reflux apparatus. Gaseous chlorine was passed through the boiling solution. After a few minutes an orange colored solid began to separate. After about 4 hours it was noticed that a further addition of chlorine did not cause separation of more solid. The solid was collected by hot filtration, washed with 500 cc of cold water and dried with air. Yield: 15 g. After crystallization of the product from 1500 cc of boiling glacial acetic acid, 12.5 g of felted orange needles, M.P. 227C. were obtained.

This compound can be usefully introduced into a photographic silver halide emulsion or into a photographic bath in ethanol of dimethylformamide solution.

(prepared according to J. Phys. Chem. 6], 265, M. M. Williams, W. S. McEvan and R. A. Henry).

20 g of lmethyl 5azotetrazole, prepared according to J.A.C.S. 76 923, R. A. Henry and W. G. Finnegan, were suspended in cc of water. 100 cc ofa 10% active chlorine sodium hypochlorite solution were added. The mixture was brought to the boil and maintained for minutes at this temperature. The resulting solution was allowed to cool in ice and was kept at 0C overnight. The yellowish solid which separated was filtered under vacuum, washed with water and dried under vacuum. Yield: 8 g. The product obtained was crystallized from 60 cc of boiling ethyl acetate. A yellow powder (6.2 g., MP. l-l22C) which according to the literature corresponds to a mixture of the cis" and trans forms, was obtained.

This compound can be usefully introduced into emulsions or photographic baths in ethanol solution.

10 g of 2-methyl-S-amino-tetrazole, suspended into 50 cc of H 0 were added to 50 cc of a 10% active chlo- 6 was washed with lOO cc of water and dried at 30C under vacuum. Yield: 5 g. M.P. 100C.

This compound can be usefully introduced into emulsions or photographic baths in ethanol solution.

Analysis: Calculated Found C% 38.99 38.49 H% 4.06 4.3! N% 56.85 56.25

EXAMPLE 8 2,2-diallyl-5 ,5 '-azotetrazole N--C N s l l CH =cH-cir -it n 3.13 g (0.025 moles) of 2-allyl-5-amino tetrazole dissolved in 50 cc of boiling water, were combined during a 10 minute period with stirring with 0.05 moles of sodium hypochlorite in a 8.5% active chlorine solution while keeping the mixture at boiling point. A crystalline rine sodium hypochlorite solution. An exothermic reyellow Solid .began immediaotely to separate The mixaction occurred and the mixture became orange in mm was rapldly cooled to 0 filters! under acuum color. The mixture was brought to the boil for 20 minwith 50 cc of cold water The residue was utes, and was then cooled in ice. After two hours the dried at Q c under l gof product were separated crystalline orange yenow solid (55 g.) was tamed, which were then dissolved in 45 cc of ethyl acefiltered off and crystallized from 45 cc of acetyl ace- The solvent Concentrated to 15 cc and tate 4 g of orange needles, MP. "0L1 were allowed to crystallize. 1.5 g of orange-yellow small neetained. dies, MP. 94-96C were obtained.

This compound can be usefully introduced into emul- Thls compound l be Introduced emul' sions or photographic baths in ethanol solution. 40 Slons or phowgraphlc baths m ethanol soluuon Analysis: Calculated Found Analysis: Calculated Found 5% 22.3% 23.3 c% 38.49 38.42 11% 4.06 4.21 N% 72.10 11.42 N% 56.89 56.28

EXAMPLE 7 EXAMPLE 9 1,1'-diallyl-5,5-azotetrazole For the compounds of example i to 8 and for the 5,5'-dichloro-2,2-azopyrine (compound C), suitable CH2 CH CH2 N a 5g solvents have been selected, and the solubility of these N L compounds at 20C in these solvents has been determined. The results are reported in the following table 1.

Table l N C--N -ca -CH -0H H Compound Solvent Solubility (weight N c Ethanol 0.0009 l Water l0 2 2% NaOH in water 10 3 2% NaOl-l in water 10 I 6.25 g of l-allyLS-amino-tetrazole (prepared accordg 3; ing to J.A.C.S. 76, 923, R. A. Henry and W. G. Finne- 6 Elha d 0.5 gan) were dissolved in 100 cc of water in a 500 cc flask 7 Ethanol equipped with a stirrer, reflux and dropping funnel. 8 While the solution was maintained at the boil, 0.1 moles of sodium hypochlonte (in a 8.5% active chlo- EXAMPLE 10 rine solution) were added over a period of 10 minutes with vigorous stirring. The mixture was allowed to cool slowly to room temperature, and was then filtered under vacuum. The orange solid which was obtained A high-sensitivity, physically seasoned, washed, and chemically sensitized silver bromo-iodide emulsion, containing 98.2 moles of bromide and 1.8 moles of iodide percent of halide, was divided in several portions to which were added respectively l'phenyl-S-mercaptotetrazole (labeled A), -methyl-benzotriazole (labeled B), and the compounds of Examples 1 to 8.

from a tungsten lamp, were developed at C in the respective developer portions for 3 minutes. 6 minutes and l2 minutes. The results of a densitometer reading of the developed samples are reported in table 3.

Each single portion was spread on a cellulose triace- 5 tate support and covered with a protective gelatin Table 3 Developer Relative Sensitivity Fog 3 min 6 min l2 min 3 min 6 min 12 min Control 100 95 90 0.21; 0.34 045 Control compound of Example N0. 2 00 73 73 0.17 0.l8 0.21

layer. Each of the resulting samples was exposed to EXAMPLE 12 light from a tungsten lamp and developed for 3 minutes E d h h at 20C in a developer of the following composition: Xample l 1 repeat? t at l samples of a seml-ammomacal, hlgh sensitlvity, silver 20 bromo-iodide emulsion, containing 98 mole bromide d2 ll'd'd 1 0D 't t Anhydrous sodium sun-e 50 8 an mo e 0 10 re were emp oye ensi ome ry re- Hydroquinone 9 g sults are reported In table 4.

Table 4 Developer Relative Sensitivity Fog 3 min 6 min 2 min 3 min 6 min l2 min Control 105 98 95 0.11; 025 036 Control compound of Example No. 2 68 76 75 0.13 0.l5 0.|8

Anhydrous sodium carbonate 50 8 Potassium bromide 3 g Water I0 1000 CC 3M Medical X-Ray Film, Type R, was exposed to gig gggg g $8 1; for the thus processed Samples blue light from a tungsten lamp and was divided into p two portions. One portion was developed for 30 min- Table 2 utes at 30C in the following developer. Compound uM/MA g Relative Sensitivity Fog Blank loo 028 Anhydrous sodium sulfite 2 g A l 100 (1-28 2-amino-5-N.N-etil-B-methan- A m 100 (1-28 sulfonamido-ethyl-toluene A 028 sulfonate 5.5 g A l0: l6 Dihydrate sodium metaborate g B 1 100 5 Sodium bromide 1.6 B loo Water to 1000 cc B 10 0.28 B 10 79 0.29 1 1.25 89 0.18 1 g i? 8-}; The remaining portion was identically developed in 2 -1 89 50 an identical developer which, however, additionally g g 5 2 3:2 contained 200 M per liter of the compound of Exam- 3 sI10- 85 0:18 P 2 3 1 75 0.17 The results of a densitometer readmg of the develw} '22 8f; oped samples are reported in table 5. 4 5.10 63 0.13 5 2.10- 75 0.20 55 Table 5 g f 32 8 if: Relative Sensitivity Fog 6 2J0 m0 (121 Control 0.23 0 10 34 0.15 532381; of 0 5.10 56 0.10 7 5.10 00 020 Example 2 0.03 a 10* 89 0.25

EXAMPLE ll EXAMPLE I4 65 Photographic material similar to that of Example 10 A quantity of the developer of Example 10 was divided into two portions. To one portion was added 50 42M of the compound of Example 2. Samples of the photographic material of Example [0, exposed to light was exposed to the light from a tungsten lamp and divided into three samples. One sample was developed in a developer of the following formula:

Metol 3 g Anhydrous sodium sulfite 50 g Hydroquinone 9 g Glutaraldehyde bisulfite 13 g Anhydrous sodium carbonate 50 g Potassium bromide 3 g Water to 1000 cc The second and third samples were identically developed, except that the developers for these samples contained respectively 50 pM per liter of the compouds of Examples 2 and 3.

Results of densitometer readings are reported in table 6.

Acetic acid to a pH 10.1

The second sample was identically developed except that the developer containing 200 p.M per liter of the compound of Example 2.

Results of -nsitometer readings are reported in table 7.

Table 7 Relative Sensitivity Fog Control 100 0.85 Control compound of Example No. 2 100 0.45

EXAMPLE 16 To samples of a medium sensitivity, physically seasoned, washed and chemically sensitized silver bromoiodide emulsion containing 97.5 moles of bromide and 2.5 mole of iodide, were added various amounts of compounds of the present invention, of red mercury iodide (a known selective desensitizer), and of l-phenyl-S-mercaptotetrazole (labeled A).

The resulting emulsions were then spread on cellulose triacetate supports, and samples of the corresponding materials were exposed to white light and to X-rays of various energy. The exposed samples were then developed for 3 minutes at 20C in the developer of Example 10.

Densitometry results are reported in table 8.

Table 8 Compound uM/MA g Relative Sensitivity Fog White R X light 67 K V 200 K V 100 100 100 0.27 l-lgl 0.5 71 100 90 0.25 Hgl 1.0 55 90 75 0.20 Hgl, 2.5 27 56 45 0.10 Hgl, 5.0 15 30 30 0.04 A 1.0 100 100 100 0.27 A 10.0 100 100 79 0.2, A 5.10 50 70 60 0.24 A 10 25 50 50 0.22 l 5.0 71 100 100 0.17 l 10 40 100 0.16 l 10 31 I00 83 0.08 l 5.10 5 50 38 0.04 2 5.10 50 89 89 0.10 2 10 25 70 70 0.08 2 2.5.10" 5 50 40 0.04 3 10 71 105 0.06 3 10 45 100 7] 0.06 3 2.5.10 10 71 50 0.04 6 10 63 100 0.08 6 10 31 89 89 0.04 7 10 50 100 89 0.08 7 10 31 E9 89 0.04 8 2 5.10 25 63 25 0.13

EXAMPLE 17 A cellulose triacetate support was thinly coated with gelatin containing powdered iron. Three samples of the resulting material, drawn at random, were each divided into four parts. On the first part a high sensitivity, silver bromo-iodide containing 98 moles of bromide and 2 mole of iodide were coated. On the other three parts of each sample, the same emulsion to which had been added respectively the compounds of Examples 1 and 2 and the 1-phenyl-S-mercapto-tetrazole (labeled A) were coated. On each element thus obtained a protective gelatin layer was coated. The resulting elements were kept 10 minutes in a cold state and were then developed 10 minutes at 20C in the developer of Example 10. The white and black points on each of the resulting elements were counted.

The results are given in table 9.

Table 9 No. of No. of No. of Compound pM/MAg Points Points Points Sample 1 Sample 2 Sample 3 150 103 89 1 102 91 Ex 1 1.5 15 17 7 Ex. 05 20 30 l 5 EXAMPLE 18 Phenidone 0.3 g Anhydrous sodium sulfite 50.0 g Hydroquinone 9.0 g

-continued Glutaraldehyde bisulfite 13.0 g Anhydrous sodium carbonate 50.0 g Potassium bromide 3.0 g Water to 1000 cc According to the time and temperature indicated in table below.

The developed material was fixed in a bath of the following composition: 10

Anhydrous sodium sulfite 50.0 g Pentahydrate sodium thiosulfate 400.0 g Glutaraldehyde bisulfite l3.0 g Water to 1000 cc and washed for a total processing time of 90 seconds. Densitometer readings are reported in table 10.

Table 10 Compound uM/MAg Developing Developing Relative Fog bath temp- Time Sensiti erature vity Control C 23 sec. 100 0.26 Ex. 2 6.25.10 35C 23 sec. 89 0.l4 Control 318C 23 sec. H2 038 Ex. 2 6.25.10" 318C 23 sec. 93 026 Control 406C 23 sec. ll2 0.56 Ex. 2 625.10" 406C 23 sec. 102 0.38

The silver halide photographic emulsions of the pres- 30 ent invention are silver chloride, silver bromide and silver iodide emulsions and mixtures thereof such as for example, silver bromoiodide and silver chlorobromide iodide. Such emulsions may include synthetic polymeric gelatin substitutes or additives, such as dextrane,

polyvinyl alcohol, polyvinyl pyrolidone, partially hy- 3 drolyzed polyvinyl acetate, polyethylacrylate, polymethylmethacrylate, polyamides, etc. The emulsions of the invention may be chemically sensitized with naturally active gelatin, by addition of chemical sensitizers such as thiourea, allylthiourea, thiocyanates, thiosulfates, etc. Sensitization may be effected by the addition of noble metals, such as gold salts. Spectral sensitizers may be employed in emulsions of the invention, such as cyanine and merocyanine dyes. Moreover, the emulsions of the invention may include such additives as color couplers, filtering dyes, surfactants, hardeners, stabilizers, additional fog-restrainers, plasticizers, oxidizing agents, developing accelerators, etc. To form a photographic element, the emulsions of the invention may be coated upon any convenient support such as polyester, cellulose acetate, and the like.

The azotriazoles and azotetrazoles of the invention may be conveniently introduced in the form of solutions into emulsions during preparation thereof. Although it is generally preferred to incorporate the azotriazole and azotetrazole compounds of the invention directly into emulsion layers, these compounds may also be incorporated into layers adjacent the emulsion layers so that the silver halide emulsions are in contact therewith. As antifog and antistain agents, the azotriazoles and azotetrazoles of the invention are preferably used in amounts ranging from about 0.03 mg. to

12 about 0.2 mg. per kilogram of emulsion, and as selective desensitizers these compounds are preferably used in amounts ranging from 3 to mg. per kilogram of emulsion.

The processing baths of the present invention, as noted previously, may be photographic pre-baths, such as those known to the art to be useful prior to treatment of a photographic emulsion with a developing solution. Predevelopment baths usually (but not necessarily) are acidic and may contain hardeners such as aldehydes and the like. The azotriazole and azotetrazole compounds of the invention may, of course, also be employed in developing baths. Such baths are normally alkaline and include one or more silver halide photographic developing agents such as hydroquinone, metol, metol-hydroquinone, phenidone, hydroquinonephenidone, and various p-phenylene diamine materials,

the latter being useful in color development processes. The processing baths of the invention (pre baths and developer baths) preferably employ from 3 to about 60 milligrams of azotriazole or azotetrazole compound per liter of solution.

What we claim is:

1. A silver halide photographic emulsion having contacted therewith at least a fog-inhibiting amount of an azotriazole or an azotetrazole.

2. The emulsion of claim 1 wherein said anti-fogging agent is a 5,5'-azotetrazole-l,l '-disodium salt.

3. The emulsion of claim 1 wherein said anti-fogging agent is a 5,5'-azotriazole.

4. The emulsion of claim 1 wherein said anti-fogging agent is a 3,3'-dimethyl-5,5'-azotriazole.

5. The emulsion of claim 1 wherein said anti-fogging agent is a 1,1'-diphenyl5,5'-azotetrazole.

6. The emulsion of claim 1 wherein said anti-fogging agent is a 1,1 '-dimethyl-5,5-azotetrazole.

7. The emulsion of claim 1 wherein said anti-fogging agent is a 2,2'-dimethyl-5,S-azotetrazole.

8. The emulsion of claim 1 wherein said anti-fogging agent is a 1,1'-diallyl-5,5'-azotetrazole.

9. The emulsion of claim 1 wherein said anti-fogging agent is a 2,2'-diallyl-5,5'-azotetrazole.

10. A method for inhibiting fog in a silver halide photographic emulsion which comprises contacting said emulsion with an azotetrazole or an azotriazole.

11. A method for inhibiting fog and stain in a silver halide emulsion which comprises contacting said emulsion with an azotriazole or an azotetrazole.

12. The emulsion of claim 1 wherein there is a fog inhibiting amount of azotriazole contacted therewith. 

1. A SILVER HALIDE PHOTOGRAPHIC EMULSION HAVING CONTACTED THEREWTIH AT LEAST A FOG-INHIBITING AMOUNT OF AN AZOTRIAZOLE OR AN AZOTETRAZOLE.
 2. The emulsion of claim 1 wherein said anti-fogging agent is a 5,5''-azotetrazole-1,1''-disodium salt.
 3. The emulsion of claim 1 wherein said anti-fogging agent is a 5,5''-azotriazole.
 4. The emulsion of claim 1 wherein said anti-fogging agent is a 3,3''-dimethyl-5,5''-azotriazole.
 5. The emulsion of claim 1 wherein said anti-fogging agent is a 1,1''-diphenyl-5,5''-azotetrazole.
 6. The emulsion of claim 1 wherein said anti-fogging agent is a 1,1''-dimethyl-5,5''-azotetrazole.
 7. The emulsion of claim 1 wherein said anti-fogging agent is a 2,2''-dimethyl-5,5''-azotetrazole.
 8. The emulsion of claim 1 wherein said anti-fogging agent is a 1,1''-diallyl-5,5''-azotetrazole.
 9. The emulsion of claim 1 wherein said anti-fogging agent is a 2,2''-diallyl-5,5''-azotetrazole.
 10. A method for inhibiting fog in a silver halide photographic emulsion which comprises contacting said emulsion with an azotetrazole or an azotriazole.
 11. A method for inhibiting fog and stain in a silver halide emulsion which comprises contacting said emulsion with an azotriazole or an azotetrazole.
 12. The emulsion of claim 1 wherein there is a fog-inhibiting amount of azotriazole contacted therewith. 